Motor having an auxiliary driven shaft

ABSTRACT

A motor unit includes a motor shaft for receiving a motor provided driving force and an auxiliary shaft for receiving an externally provided driving force. A first torque transmission path transfers the externally provided driving force to a drive mechanism and a second torque transmission path transfers the motor provided driving force also to the drive mechanism. A first one way drive is provided in the first torque transmission path between the auxiliary shaft and the drive mechanism such that when the drive mechanism is being driven by the motor provided driving force through the second torque transmission path, the auxiliary shaft is able to freewheel. The motor unit can drive any apparatus where the externally provided driving force is provided by manually operable pedals fixed for rotation with the auxiliary shaft.

FIELD OF THE INVENTION

The invention relates to a motor having an auxiliary driven shaft andparticularly, but not exclusively, to a pedal driven apparatus which canbe manually propelled, but which includes a motor unit for also causingforward propulsion of the apparatus. The invention also relatesparticularly, but not exclusively, to pedal driven wheeled apparatusesor vehicles such as bicycles having an electric motor powered by abattery pack carried on the vehicle.

BACKGROUND OF THE INVENTION

It is known to provide some manually propellable wheeled vehicles orapparatuses such as bicycles with a motor unit to assist a user inpowering the apparatus, especially up sloping terrain, e.g. hills,although the motor unit may sometimes be used by itself to power thebicycle over any terrain.

It is also known to utilize an in-wheel motor in an electric motorassisted bicycle such that a transmission can be omitted and theresulting apparatus is easy and simple to manufacture. For such a knownelectric motor assisted bicycle using an in-wheel motor, it can bemanufactured by simply replacing a hub of one wheel with an in-wheelmotor, while the pedals drive the rear wheel through a sprocket and achain in a generally conventional manner. In such an arrangement, nomotor drive force need be transferred through the bicycle chain.Therefore, a pedal driving force and a motor driving force are deliveredquite separately from each other.

One consequence of the known in-wheel motor arrangement is that it isnot feasible for an in-wheel electric motor assisted bicycle to bedeveloped with additional functions such as gear shifting, operatingwith a clutch, functioning as an exercise bicycle, or using the motor togenerate power, i.e. it does not afford easy expansion of its functions.It also creates production and assembly problems as well as replacementparts problems. Where an in-wheel motor fails or requires maintenance,for example, it requires the wheel to be removed thus disabling thebicycle. Under some motor failure or maintenance conditions, it may nolonger be possible to rotate the wheel accommodating the in-wheel motorsuch that it is not even possible to propel the bicycle under manuallyapplied pedal power.

In addition to the known electric bicycle using an in-wheel motor, thereis at least one other type of electric bicycle which uses awheel-driving motor. However, in this type of electric bicycle, a motordriving force and a pedal driving force are also separately deliveredfrom each other. This type of electric bicycle has similar disadvantagesin that gear shifting can not be easily realized using a rear wheeltransmission when the electric bicycle is being propelled using thewheel-driving motor.

The foregoing are just some of the common problems encountered withconventional hybrid motor assisted pedal driven apparatuses such asbicycles.

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved motor unit.

Another object of the invention is to provide an improved electric motorfor a motor assisted bicycle.

Another object of the invention is to mitigate or obviate to some degreeone or more problems associated with known motor units.

One skilled in the art will derive from the following description otherobjects of the invention. Therefore, the foregoing statements of objectare not exhaustive and serve merely to illustrate some of the manyobjects of the present invention.

In a first main aspect of the invention, there is provided a motor unitcomprising: a motor shaft for receiving a motor provided driving force;an auxiliary shaft for receiving an externally provided driving force; afirst torque transmission path for transferring the externally provideddriving force to a drive mechanism; a second torque transmission pathfor transferring the motor provided driving force to said drivemechanism; wherein a first one way drive means is provided in the firsttorque transmission path between the auxiliary shaft and the drivemechanism such that when the drive mechanism is being driven by themotor provided driving force through the second torque transmissionpath, the auxiliary shaft is able to freewheel. The externally provideddriving force may be provided by another motor or any other suitabledrive means coupled to impart drive to said auxiliary shaft.

Preferably, the motor shaft is arranged concentrically around theauxiliary shaft such that the auxiliary shaft is freely accommodatedthrough a hollow bore of the motor shaft and such that their axes ofrotation are parallel. The auxiliary shaft and the motor shaft may sharethe same axis of rotation.

Preferably, the first torque transmission path comprises the auxiliaryshaft for receiving an externally provided driving force and the firstone way drive means, wherein the first one way drive means mechanicallycouples the auxiliary shaft to the drive mechanism such that the firstone way drive means transfers the externally provided driving force tothe drive mechanism and wherein the first one way drive means allows theauxiliary shaft to freewheel when the drive mechanism is being driven bythe motor shaft. The first one way drive means may comprise a freewheeldevice.

Preferably, the second torque transmission path comprises the motorshaft and a gear mechanism mechanically coupling the motor shaft to thedrive mechanism, wherein the gear mechanism has a reduction gear ratioand operates to transfer the motor provided driving force from the motorshaft to the drive mechanism at said reduction gear ratio.

Preferably, the gear mechanism comprises a planetary gear mechanismhaving a planet gear whose axis of rotation is offset by a predeterminedamount with respect to the axis of rotation of the motor shaft. Theplanet gear may be rotatably supported on an eccentric wheel whereby theplanet gear is made to rotate as the eccentric wheel rotates and wherebythe position of the axis of rotation of the planet gear changes relativeto the axis of rotation of the motor shaft as the planet gear rotatessuch that the varying position of the axis of rotation of the planetgear defines a circle centred on the axis of rotation of the motorshaft, said circle having a radius equal to the predetermined offsetamount. Furthermore, the planet gear may have a smaller diameter than aninternal ring gear within which it locates for rotation therewithin, theinternal ring gear being fixed in position and having a central axisco-incident with the axis of rotation of the motor shaft, the planetgear having a smaller number of teeth than the internal ring gear. Theplanet gear may be rotatably supported on the eccentric wheel by abearing.

Preferably, a planet gear carrier of the planetary gear mechanism isconfigured to transfer the motor provided driving force to the drivemechanism. The planetary gear mechanism may include a counterbalancemember which is configured to counterbalance an imbalance of weightcaused by the offsetting of the planet gear with respect to the axis ofrotation of the motor shaft. The counterbalance member may comprise agenerally semi-circular weighted member which is arranged to rotate withthe planet gear so as to counterbalance the planet gear when the planetgear is rotating.

Alternatively, the planetary gear mechanism does not include a weightedcounterbalance member, but comprises first and second identical planetgears arranged half a revolution out of phase with each other such thatsaid first and second planet gears counterbalance each other onrotation. The first and second planet gears may be located for rotationhalf a revolution out of phase with each other within a common, singleinternal ring gear. Each of the first and second planet gears may besupportably mounted on respective first and second eccentric wheels.

Preferably, the planet gear carrier is affixed to the drive mechanismfor rotation therewith. The planet gear carrier may also be affixed toan output member of the first one way drive means for rotationtherewith, whereby the externally provided driving force is transferredvia the first torque transmission path to the motor shaft through theplanetary gear mechanism as well as to the drive mechanism.

Alternatively, the gear mechanism comprises a toothless planetary gearmechanism having a toothless planet gear whose axis of rotation isoffset by a predetermined amount with respect to the axis of rotation ofthe motor shaft and wherein the reduction gear ratio of the toothlessplanetary gear mechanism is defined by a relationship between therespective diameters of the toothless planet gear and a toothlessinternal ring gear within which the planet gear is located for rotation,the toothless planet gear having a smaller diameter than the toothlessinternal ring gear. The toothless planet gear may be rotatably supportedon an eccentric wheel whereby the toothless planet gear is made torotate as the eccentric wheel rotates and whereby the position of theaxis of rotation of the toothless planet gear changes relative to theaxis of rotation of the motor shaft as the toothless planet gear rotatessuch that the varying position of the axis of rotation of the toothlessplanet gear defines a circle centred on the axis of rotation of themotor shaft, said circle having a radius equal to the predeterminedoffset amount. The toothless internal ring gear may be fixed in positionand has a central axis co-incident with the axis of rotation of themotor shaft. The toothless planet gear may be rotatably supported on theeccentric wheel by a bearing.

Preferably, a planet gear carrier of the toothless planetary gearmechanism is configured to transfer the motor provided driving force tothe drive mechanism.

Preferably, the toothless planetary gear mechanism includes acounterbalance member which is configured to counterbalance an imbalanceof weight caused by the offsetting of the toothless planet gear withrespect to the axis of rotation of the motor shaft. The counterbalancemember may comprise a generally semi-circular weighted member which isarranged to rotate with the toothless planet gear so as tocounterbalance the toothless planet gear when the toothless planet gearis rotating.

Alternatively, the toothless planetary gear mechanism does not include aweighted counterbalance member, but comprises first and second identicaltoothless planet gears arranged half a revolution out of phase with eachother such that said first and second toothless planet gearscounterbalance each other on rotation. The first and second toothlessplanet gears may be located for rotation half a revolution out of phasewith each other within a common, single toothless internal ring gear.Each of the first and second toothless planet gears may be supportablymounted on respective first and second eccentric wheels.

Preferably, the planet gear carrier is affixed to the drive mechanismfor rotation therewith. The planet gear carrier may also be affixed toan output member of the first one way drive means for rotationtherewith, whereby the externally provided driving is transferred viathe first torque transmission path to the motor shaft through thetoothless planetary gear mechanism as well as to the drive mechanism.

Preferably, the toothless planet gear is rotatably supported on theeccentric wheel with its axis of rotation is offset by a predeterminedamount with respect to the axis of rotation of the motor shaft andlocated within the toothless internal ring gear to engage a toothlessinner ring gear surface by heating the toothless internal ring gear andshrink fitting it over the toothless planet gear. The first and secondtoothless planet gears may be rotatably supported respectively on thefirst and second eccentric wheels with their axes of rotation offset bya predetermined amount with respect to the axis of rotation of the motorshaft and located within a common, single toothless internal ring gearfor rotation half a revolution out of phase with each other to engage atoothless inner ring gear surface by heating the toothless internal ringgear and shrink fitting it over the first and second toothless planetgears.

Preferably, a second one way drive means is provided in the secondtorque transmission path between the motor shaft and the drive mechanismsuch that when the drive mechanism is being driven by the externallyprovided driving force through the first torque transmission path, themotor shaft is not caused to rotate. The second one way drive means maycomprise at least one ratchet member moveably disposed on the planetgear carrier and arranged to engage a rack of a ratchet wheel fixed torotate with the drive mechanism. The at least one ratchet member mayhave associated therewith means for resiliently biasing a free end ofsaid ratchet member outwardly from a surface of the planet gear carriersuch that said free end of the ratchet member engages a tooth in therack of the ratchet wheel.

In another aspect of the invention, the motor unit comprises a part of apedal driven apparatus.

In another aspect of the invention, the motor unit is an electric motorpowered by a battery pack carried on a pedal driven apparatus.

In a second main aspect of the invention, there is provided a pedaldriven apparatus having a motor unit according to the first main aspect,wherein said externally provided driving force is a manually provideddriving force provided by manually operable pedals of said apparatuswhich are fixed for rotation with the auxiliary shaft, said auxiliaryshaft comprising a pedal spindle; and wherein said drive mechanismcomprises a sprocket, said first torque transmission path being arrangedto transfer the manually provided driving force to said sprocket andsaid second torque transmission path being arranged to transfer themotor provided driving force to said sprocket; and wherein the first oneway drive means is provided in the first torque transmission pathbetween the pedal spindle and the sprocket such that when the sprocketis being driven by the motor provided driving force through the secondtorque transmission path, the pedal spindle is able to freewheel.

In a third main aspect of the invention, there is provided a pedaldriven apparatus comprising: manually operable pedals fixed for rotationwith a pedal spindle for receiving a manually provided driving force; amotor having a shaft for receiving a motor provided driving force; afirst torque transmission path for transferring the manually provideddriving force to a sprocket of the pedal driven apparatus; a secondtorque transmission path for transferring the motor provided drivingforce to said sprocket of the pedal driven apparatus; wherein a firstone way drive means is provided in the first torque transmission pathbetween the pedal spindle and the sprocket such that when the sprocketis being driven by the motor provided driving force through the secondtorque transmission path, the pedal spindle is able to freewheel.

An advantage of this arrangement is that it is not necessary to providea freewheel sprocket on the rear wheel of a bicycle having a motor andsprocket assembly as defined by the third main aspect of the inventionfor a pedal driven apparatus. This is because the first one way drivemeans provides this function in addition to enabling the pedal spindleto freewheel when the motor drive is operating.

The motor may be arranged concentrically around the pedal spindle suchthat the pedal spindle is freely accommodated through a hollow bore ofthe motor shaft and such that their axes of rotation are parallel. Thepedal spindle and the motor shaft preferably share the same axis ofrotation.

This arrangement results in a neat and compact integration of the motorwith the pedal spindle and sprocket assembly.

The first torque transmission path may comprise the manually operablepedals, the pedal spindle to which the pedals are affixed for rotationtherewith, and the first one way drive means, wherein the first one waydrive means mechanically couples the pedal spindle to the sprocket suchthat the first one way drive means transfers the manually provideddriving force applied to the pedals to the sprocket to cause rotation ofthe sprocket and wherein the first one way drive means allows the pedalspindle to freewheel when the sprocket is being driven by the motorshaft. Preferably, the first one way drive means comprises a freewheeldevice such as an over-running bearing or an over-running clutch or anydevice suitable for enabling drive to be applied through an outputmember of the one way drive means, but for an input member to freewheelwhen no drive is being transferred through said first one way drivemeans.

The first one way drive means may be associated with one of the manuallyoperable pedals affixed to the pedal spindle for rotation therewith,said one of the pedals comprising one of two pedals which is affixed toan end of the pedal spindle on a sprocket side of the pedal drivenapparatus.

The second torque transmission path may comprise the motor shaft and agear mechanism mechanically coupling the motor shaft to the sprocket,wherein the gear mechanism has a reduction gear ratio and operates totransfer the motor provided driving force from the motor shaft to thesprocket at said reduction gear ratio. The gear mechanism may comprise aplanetary gear mechanism having a planet gear whose axis of rotation isoffset by a predetermined amount with respect to the axis of rotation ofthe motor shaft.

This allows a high speed motor to be employed whereby the gear mechanismapplies a suitable reduction gear ratio to the output shaft of the motorto rotate the sprocket at high torque and low speed (relatively speakingwhen compared to the motor shaft speed of rotation).

The planet gear may be rotatably supported on an eccentric wheel wherebythe planet gear is made to rotate as the eccentric wheel rotates andwhereby the position of the axis of rotation of the planet gear changesrelative to the axis of rotation of the motor shaft as the planet gearrotates such that the varying position of the axis of rotation of theplanet gear defines a circle centred on the axis of rotation of themotor shaft, said circle having a radius equal to the predeterminedoffset amount. The planet gear may have a smaller diameter than aninternal ring gear within which it locates for rotation therewithin, theinternal ring gear being fixed in position and having a central axisco-incident with the axis of rotation of the motor shaft, the planetgear having a smaller number of teeth than the internal ring gear. Theplanet gear may be rotatably supported on the eccentric wheel by abearing or a bush.

The planet gear rotates around the inner toothed surface of the innerring gear such that the outer toothed surface of the planet gear mesheswith only a small number of teeth of the inner ring gear at any point oftime.

A planet gear carrier of the planetary gear mechanism may be configuredto transfer the motor provided driving force to the sprocket.

Using a planet gear carrier of the gear mechanism in this way provides aneat and efficient way of mechanically transferring the motor drivingforce to the sprocket assembly.

The planetary gear mechanism may include a counterbalance member whichis configured to counterbalance an imbalance of weight caused by theoffsetting of the planet gear with respect to the axis of rotation ofthe motor shaft. The counterbalance member may comprise a generallysemi-circular weighted member which is arranged to rotate with theplanet gear so as to counterbalance the planet gear when the planet gearis rotating.

Preferably, the planetary gear mechanism does not include a weightedcounterbalance member, but comprises first and second identical planetgears arranged half a revolution out of phase with each other such thatsaid first and second planet gears counterbalance each other onrotation. Preferably also, the first and second planet gears are locatedfor rotation half a revolution out of phase with each other within acommon, single internal ring gear. Each of the first and second planetgears may be supportably mounted on respective first and secondeccentric wheels.

The use of two out of phase planet gears negates the need to provide aweighted counterbalance member and provides a balanced system whichtransfers motor driving force to the sprocket assembly more efficientlyand quietly than the foregoing arrangement including a weightedcounterbalance.

The planet gear carrier may be affixed to the sprocket for rotationtherewith. The planet gear carrier may also be affixed to an outputmember of the first one way drive means for rotation therewith, wherebythe manually provided driving force applied to the pedals is transferredvia the first torque transmission path to the motor shaft through theplanetary gear mechanism as well as to the sprocket.

In this arrangement, a user can, through use of a control mounted, forexample, on the handlebar of the bicycle or any manually accessiblelocation on the pedal driven apparatus, control the motor to act as apower generator. The user may operate a switch to control the motor touse mechanical power being provided manually through the pedals andwhich causes the motor shaft to rotate to generate electric power forrecharging the motor battery pack or powering lights, for example.

Preferably, the gear mechanism comprises a toothless planetary gearmechanism having a toothless planet gear whose axis of rotation isoffset by a predetermined amount with respect to the axis of rotation ofthe motor shaft and wherein the reduction gear ratio of the toothlessplanetary gear mechanism is defined by a relationship between therespective diameters of the toothless planet gear and a toothlessinternal ring gear within which the planet gear is located for rotation,the toothless planet gear having a smaller diameter than the toothlessinternal ring gear.

The advantage of a toothless planetary gear mechanism is one ofquietness. The lack of gear teeth and the reliance on contact betweengenerally smooth surfaces to effect a transfer of power from the motorto the sprocket results in very quiet operation and more efficient powertransfer as there is no slippage between gear teeth as can occur intoothed gear mechanisms.

The toothless planet gear may be rotatably supported on an eccentricwheel whereby the toothless planet gear is made to rotate as theeccentric wheel rotates and whereby the position of the axis of rotationof the toothless planet gear changes relative to the axis of rotation ofthe motor shaft as the toothless planet gear rotates such that thevarying position of the axis of rotation of the toothless planet geardefines a circle centred on the axis of rotation of the motor shaft,said circle having a radius equal to the predetermined offset amount.

The toothless internal ring gear may be fixed in position and may have acentral axis co-incident with the axis of rotation of the motor shaft.

The toothless planet gear may be rotatably supported on the eccentricwheel by a bearing or a bushing.

A planet gear carrier of the toothless planetary gear mechanism may beconfigured to transfer the motor provided driving force to the sprocket.

The toothless planetary gear mechanism may includes a counterbalancemember which is configured to counterbalance an imbalance of weightcaused by the offsetting of the toothless planet gear with respect tothe axis of rotation of the motor shaft. The counterbalance member maycomprise a generally semi-circular weighted member which is arranged torotate with the toothless planet gear so as to counterbalance thetoothless planet gear when the toothless planet gear is rotating.

Preferably, the toothless planetary gear mechanism does not include aweighted counterbalance member, but comprises first and second identicaltoothless planet gears arranged half a revolution out of phase with eachother such that said first and second toothless planet gearscounterbalance each other on rotation. Preferably, the first and secondtoothless planet gears are located for rotation half a revolution out ofphase with each other within a common, single toothless internal ringgear. Each of the first and second toothless planet gears may besupportably mounted on respective first and second eccentric wheels.

The planet gear carrier may be affixed to the sprocket for rotationtherewith. The planet gear carrier may also be affixed to an outputmember of the first one way drive means for rotation therewith, wherebythe manually provided driving force applied to the pedals is transferredvia the first torque transmission path to the motor shaft through thetoothless planetary gear mechanism as well as to the sprocket.

The toothless planet gear may be rotatably supported on the eccentricwheel with its axis of rotation is offset by a predetermined amount withrespect to the axis of rotation of the motor shaft and located withinthe toothless internal ring gear such that its outer surface engages atoothless inner ring gear inner surface by heating the toothlessinternal ring gear and shrink fitting it over the toothless planet gear.The inner surface of the internal ring gear and/or the outer surface ofthe planet gear may be roughened to enhance the coefficient of frictionacting between said engaged surfaces at their line of contact.

The first and second toothless planet gears are preferably rotatablysupported respectively on the first and second eccentric wheels withtheir axes of rotation offset by a predetermined amount with respect tothe axis of rotation of the motor shaft and located within a common,single toothless internal ring gear for rotation half a revolution outof phase with each other to engage a toothless inner ring gear surfaceby heating the toothless internal ring gear and shrink fitting it overthe first and second toothless planet gears. The inner surface of theinternal ring gear and/or the outer surfaces of the planet gear may beroughened to enhance the coefficient of friction acting between saidengaged surfaces at their lines of contact.

Preferably, a second one way drive means is provided in the secondtorque transmission path between the motor shaft and the sprocket suchthat when the sprocket is being driven by the manually provided drivingforce through the first torque transmission path, the motor shaft is notcaused to rotate. The second one way drive means may comprise at leastone ratchet member moveably disposed on the planet gear carrier andarranged to engage a rack of a ratchet wheel fixed to rotate with thesprocket. The at least one ratchet member may have associated therewithmeans for resiliently biasing a free end of said ratchet memberoutwardly from a surface of the planet gear carrier such that said freeend of the ratchet member engages a tooth in the rack of the ratchetwheel.

Preferably, the pedal driven apparatus comprises a bicycle, although thepresent invention is not limited to bicycles, but can be applied to anypedal driven apparatus.

The motor is preferably an electric motor powered by a battery packcarried on the pedal driven apparatus.

In a fourth main aspect of the invention, there is provided a motor fora pedal driven apparatus comprising: a shaft for receiving a motorprovided driving force; and a gear mechanism mechanically coupling themotor shaft to a sprocket of the pedal driven apparatus, wherein thegear mechanism has a reduction gear ratio and operates to transfer themotor provided driving force from the motor shaft to the sprocket atsaid reduction gear ratio and wherein the motor is arrangedconcentrically around a pedal spindle of the pedal driven apparatus suchthat the pedal spindle is freely accommodated through a hollow bore ofthe motor shaft and such that their axes of rotation are parallel.

Preferably, the pedal spindle and the motor shaft share the same axis ofrotation.

The gear mechanism preferably comprises a planetary gear mechanismhaving a planet gear whose axis of rotation is offset by a predeterminedamount with respect to the axis of rotation of the motor shaft. Theplanet gear is preferably rotatably supported on an eccentric wheelwhereby the planet gear is made to rotate as the eccentric wheel rotatesand whereby the position of the axis of rotation of the planet gearchanges relative to the axis of rotation of the motor shaft as theplanet gear rotates such that the varying position of the axis ofrotation of the planet gear defines a circle centred on the axis ofrotation of the motor shaft, said circle having a radius equal to thepredetermined offset amount.

Preferably, the planet gear has a smaller diameter than an internal ringgear within which it locates for rotation therewithin, the internal ringgear being fixed in position and having a central axis co-incident withthe axis of rotation of the motor shaft, the planet gear having asmaller number of teeth than the internal ring gear. Preferably, theplanet gear is rotatably supported on the eccentric wheel by a bearing.

Preferably, a planet gear carrier of the planetary gear mechanism isconfigured to transfer the motor provided driving force to the sprocketof the pedal driven apparatus.

The planetary gear mechanism may include a counterbalance member whichis configured to counterbalance an imbalance of weight caused by theoffsetting of the planet gear with respect to the axis of rotation ofthe motor shaft. The counterbalance member may comprise a generallysemi-circular weighted member which is arranged to rotate with theplanet gear so as to counterbalance the planet gear when the planet gearis rotating.

Preferably, the planetary gear mechanism does not include a weightedcounterbalance member, but comprises first and second identical planetgears arranged half a revolution out of phase with each other such thatsaid first and second planet gears counterbalance each other onrotation. Preferably, the first and second planet gears are located forrotation half a revolution out of phase with each other within a common,single internal ring gear. Preferably, the first and second planet gearsare supportably mounted on respective first and second eccentric wheels.

Preferably, the gear mechanism comprises a toothless planetary gearmechanism having a toothless planet gear whose axis of rotation isoffset by a predetermined amount with respect to the axis of rotation ofthe motor shaft and wherein the reduction gear ratio of the toothlessplanetary gear mechanism is defined by a relationship between therespective diameters of the toothless planet gear and a toothlessinternal ring gear within which the planet gear is located for rotation,the toothless planet gear having a smaller diameter than the toothlessinternal ring gear.

Preferably, the toothless planet gear is rotatably supported on aneccentric wheel whereby the toothless planet gear is made to rotate asthe eccentric wheel rotates and whereby the position of the axis ofrotation of the toothless planet gear changes relative to the axis ofrotation of the motor shaft as the toothless planet gear rotates suchthat the varying position of the axis of rotation of the toothlessplanet gear defines a circle centred on the axis of rotation of themotor shaft, said circle having a radius equal to the predeterminedoffset amount.

Preferably, the toothless internal ring gear is fixed in position andhas a central axis co-incident with the axis of rotation of the motorshaft.

Preferably, the toothless planet gear is rotatably supported on theeccentric wheel by a bearing or a bushing.

Preferably, the planet gear carrier of the toothless planetary gearmechanism is configured to transfer the motor provided driving force tothe sprocket.

The toothless planetary gear mechanism may include a counterbalancemember which is configured to counterbalance an imbalance of weightcaused by the offsetting of the toothless planet gear with respect tothe axis of rotation of the motor shaft.

Preferably, the toothless planetary gear mechanism does not include aweighted counterbalance member, but comprises first and second identicaltoothless planet gears arranged half a revolution out of phase with eachother such that said first and second toothless planet gearscounterbalance each other on rotation.

Preferably, the first and second toothless planet gears are located forrotation half a revolution out of phase with each other within a common,single toothless internal ring gear. Each of the first and secondtoothless planet gears may be supportably mounted on respective firstand second eccentric wheels.

The toothless planet gear may be rotatably supported on the eccentricwheel with its axis of rotation offset by a predetermined amount withrespect to the axis of rotation of the motor shaft and located withinthe toothless internal ring gear to engage a toothless inner ring gearsurface by heating the toothless internal ring gear and shrink fittingit over the toothless planet gear.

Preferably, the first and second toothless planet gears are rotatablysupported respectively on the first and second eccentric wheels withtheir axes of rotation offset by a predetermined amount with respect tothe axis of rotation of the motor shaft and located within a common,single toothless internal ring gear for rotation half a revolution outof phase with each other to engage a toothless inner ring gear surfaceby heating the toothless internal ring gear and shrink fitting it overthe first and second toothless planet gears.

Preferably, a one way drive means is provided between the motor shaftand the sprocket such that when the sprocket is being driven by amanually provided driving force through pedals of the pedal drivenapparatus, the motor shaft is not caused to rotate.

In a fifth main aspect of the invention, there is provided a sprocketassembly for a pedal driven apparatus, comprising: a sprocket; firstmeans for mechanically coupling the sprocket to a pedal driven pedalspindle; and second means for mechanically coupling the sprocket to anoutput shaft of a motor, wherein the first mechanical coupling meansincludes a first one way drive means coupling the pedal spindle and thesprocket such that the first one way drive means transfers a manuallyprovided driving force applied to the pedals of the pedal drivenapparatus to the sprocket to cause rotation of the sprocket and allowsthe pedal spindle to freewheel when the sprocket is being driven by themotor output shaft.

Preferably, the second mechanical coupling means is configured tomechanically couple the sprocket to the output shaft of the motor wherethe motor is arranged concentrically around the pedal spindle of thepedal driven apparatus such that the pedal spindle is freelyaccommodated through a hollow bore of the motor shaft and such thattheir axes of rotation are parallel.

Preferable, the second mechanical coupling means comprises a gearmechanism mechanically coupling the motor output shaft to the sprocket,wherein the gear mechanism has a reduction gear ratio and operates totransfer a motor provided driving force from the motor output shaft tothe sprocket at said reduction gear ratio. The gear mechanism preferablycomprises a planetary gear mechanism having a planet gear whose axis ofrotation is offset by a predetermined amount with respect to the axis ofrotation of the motor output shaft.

Preferably, the planet gear is rotatably supported on an eccentric wheelwhereby the planet gear is made to rotate as the eccentric wheel rotatesand whereby the position of the axis of rotation of the planet gearchanges relative to the axis of rotation of the motor output shaft asthe planet gear rotates such that the varying position of the axis ofrotation of the planet gear defines a circle centred on the axis ofrotation of the motor output shaft, said circle having a radius equal tothe predetermined offset amount.

A planet gear carrier of the planetary gear mechanism may be configuredto transfer the motor provided driving force to the sprocket. The planetgear carrier may be affixed to the sprocket for rotation therewith. Theplanet gear carrier may also be affixed to an output member of the firstone way drive means for rotation therewith, whereby the manuallyprovided driving force applied to the pedals is transferred to the motoroutput shaft through the planetary gear mechanism as well as to thesprocket.

Preferably, the second mechanical coupling means includes a second oneway drive means coupling the motor output shaft and the sprocket suchthat when the sprocket is being driven by a manually provided drivingforce applied to the pedals of the pedal driven apparatus, the motorshaft is not caused to rotate. The second one way drive means maycomprise at least one ratchet member moveably disposed on the planetgear carrier and arranged to engage a rack of a ratchet wheel fixed torotate with the sprocket.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further features of the present invention will beapparent from the following description of preferred embodiments whichare provided by way of example only in connection with the accompanyingfigures, of which:

FIG. 1 is a structural schematic view of a first embodiment of a motorand sprocket assembly for a pedal driven apparatus according to theinvention;

FIG. 2 is a sectional view taken along the line II-II of FIG. 1;

FIG. 3 is an enlarged sectional view taken along the line III-III ofFIG. 1;

FIG. 4 is an exploded perspective view of the embodiment of FIG. 1;

FIG. 5 is a structural schematic view of a second embodiment of a motorand sprocket assembly for a pedal driven apparatus according to theinvention;

FIG. 6 is an exploded perspective view of a third embodiment of a motorand sprocket assembly for a pedal driven apparatus according to theinvention;

FIG. 7 is a structural schematic view of a fourth embodiment of a motorand sprocket assembly for a pedal driven apparatus according to theinvention;

FIG. 8 is a sectional view taken along the line VIII-VIII of FIG. 7;

FIG. 9 is an exploded perspective view of the embodiment of FIG. 7; and

FIG. 10 is a schematic view of a pedal driven apparatus having a motorand sprocket assembly according to any of the embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The invention primarily concerns motorized bicycles, although theinvention is applicable to any hybrid apparatus having pedals to providea human power input and a motor to provide a mechanical power input. Amotorized bicycle is a bicycle with an attached motor used to power thevehicle, or to assist with pedaling. Sometimes classified as a motorvehicle, or a class of hybrid vehicle, motorized bicycles may be poweredby different types of engines. Motorized bicycles are distinguished frommotorcycles by being capable of being powered by pedals alone ifrequired. The actual usage of the pedals varies widely according to thetype of vehicle. Some can be propelled by the motor alone if the riderchooses not to pedal. Those known as power-assist bikes have the pedalsas the main form of propulsion with the motor used to give a bit ofextra power, especially uphill. Many motorized bicycles are based onstandard bicycle frame designs and technologies.

In a parallel hybrid motorized bicycle, human and motor inputs aremechanically coupled either in the bottom bracket, the rear or the frontwheel, whereas in a (mechanical) series hybrid cycle, the human andmotor inputs are coupled through differential gearing. In a (electronic)series hybrid cycle, human power is converted into electricity and isfed directly into the motor and mostly additional electricity issupplied from a battery.

“Pedelec” is a European term that generally refers to an electricbicycle that incorporates a torque and/or a speed sensor and/or a powercontroller that delivers a proportionate level of assist and only runswhen the rider pedals.

The present invention is applicable to all of the above forms of bicyclehaving both a motor unit and pedals, but where the motor is arranged inclose proximity to the sprocket assembly, preferably with the motorbeing arranged concentrically with the pedal spindle such that the pedalspindle is accommodated within a hollow shaft of the motor.

It is to be understood in the following description that the terms“sprocket” or “drive sprocket” are to be taken to mean any rotationalcomponent capable of transferring a driving force to another rotationalcomponent and includes, but is not limited to, toothed sprockets forengaging drive chains, belt pulleys for engaging drive belts, or gearwheels for engaging other gear wheels or gear trains.

In the following description, reference will be made to a bicycle as anexample of a pedal driven apparatus, but it will be understood that theinvention is not limited to bicycles and the following description isequally applicable to other types of pedal driven apparatuses such astricycles, pedalos (pedal boat), or the like or to other devices orappliances driven by a motor unit.

Referring to FIGS. 1 to 4, shown is a first embodiment of a motor andsprocket assembly according to the invention. A bicycle having saidmotor and sprocket assembly comprises means for providing an externallyprovided driving force in the form of manually operable pedals 10 fixedfor rotation with an auxiliary shaft comprising a pedal spindle 1 forreceiving a manually provided driving force and a motor 5 having a shaft4 for receiving a motor provided driving force. A first torquetransmission path is provided for transferring the manually provideddriving force to a drive mechanism comprising a sprocket 16 of the pedaldriven apparatus and a second torque transmission path is provided fortransferring the motor provided driving force to said sprocket 16 of thepedal driven apparatus. A first one way drive means 13 is provided inthe first torque transmission path between the pedal spindle 1 and thesprocket 16 such that, when the sprocket is being driven by the motorprovided driving force through the second torque transmission path, thepedal spindle 1 is able to freewheel.

An advantage of this arrangement is that it is not necessary to providea freewheel sprocket on the rear wheel of the bicycle. This is becausethe first one way drive means 13 provides this function in addition toenabling the pedal spindle 1 to freewheel when the motor drive isoperating.

The first torque transmission path comprises the manually operablepedals 10, the pedal spindle 1 to which the pedals 10 are affixed forrotation therewith, and the first one way drive means 13. The first oneway drive means 13 mechanically couples the pedal spindle 1 to thesprocket 16 such that the first one way drive means 13 transfers themanually provided driving force applied to the pedals 10 to the sprocket16 to cause rotation of the sprocket. The first one way drive means 13also allows the pedal spindle 1 to freewheel when the sprocket 16 isbeing driven by the motor shaft 4. The first one way drive means 13 maycomprise a freewheel device such as an over-running bearing or anover-running clutch or any device suitable for enabling drive to beapplied through an output member of the one way drive means, but for aninput member to freewheel when no drive is being transferred throughsaid first one way drive means 13.

The second torque transmission path comprises the motor shaft 4 and agear mechanism housed in a casing 7 mechanically coupling the motorshaft 4 to the sprocket 16. The gear mechanism has a reduction gearratio and operates to transfer the motor provided driving force from themotor shaft 4 to the sprocket 16 at said reduction gear ratio. The gearmechanism may comprise a planetary gear mechanism having a planet gear20 whose axis of rotation is offset by a predetermined amount withrespect to the axis of rotation of the motor shaft 4.

This allows a high speed motor to be employed whereby the gear mechanismapplies a suitable reduction gear ratio to the output shaft of the motorto rotate the sprocket at high torque and low speed (relatively speakingwhen compared to the motor shaft speed of rotation).

As shown more explicitly in FIGS. 1 to 4, the motor and sprocketassembly comprises: the motor 5, the motor rotor hollow shaft 4supported by bearings 3 and 6, an end cover at one end of the motor 5,i.e. the casing 7 of the planetary gear mechanism, an internal gear ring8 fixed within the casing 7 of the planetary gear mechanism; aneccentric wheel 22 fixed around the hollow shaft 4 of the motor 5, and aflat key 23 disposed between the hollow shaft 4 and the eccentric wheel22 for transmitting torque. The planet gear 20 is fit around the outercircumference of the eccentric wheel 22 by means of a bearing 21, forrotation with the eccentric wheel 22, and engaged with the teeth of theinternal gear ring 8. Four circular holes 19 are provided on a sidesurface of the planet gear 20. A planet gear carrier 11 is supportedwithin the casing 7 by means of a bearing 9, and is provided with fourpins 17 on a side surface facing the planet gear 20. Bushings 18 areprovided around the pins 17 and inserted into the four circular holes 19on the side surface of the planet gear 20. The function of the four pins17 and the bushings 18 inserted into the four circular holes 19 on theplanet gear carrier 11 is to transfer drive from the planet gear 20 tothe planet gear carrier 11 as the planet gear 20 rotates. The bushings18 revolve around the pins 17 to accommodate rotation of the planet gear20. The holes have a diameter larger than the diameter of the pins 17 toaccommodate eccentric movement of the planet gear 20 with respect to theaxis of rotation of the motor shaft 4.

To effect the transfer of a motor driving force from the planet gear 20to the planet gear carrier 11, ratchet seats are arranged on an outerside of the planet gear carrier 11 and ratchets 15 moveably disposed onthe ratchet seats and engaged with an inner surface of a ratchet wheel12 which is affixed to the sprocket 16. The pedal central spindle 1 isfreely disposed in the hollow shaft 4 of the motor 5 and is mountedcoaxially with the motor shaft 4. The pedal central spindle 1 issupported in the hollow shaft 4 of the motor and the planet gear carrier11 by means of bearings 2 and 14 respectively. The pedal cranks 10 aredisposed at the ends of the pedal central spindle 1. Associated with thepedal crank 10 on a sprocket side of the assembly is the first one waydrive means comprising a one-way freewheel 13 fixed on said pedal crank10. A side surface of the ratchet wheel 12 is fixed on a flange of theone-way freewheel 13, and the sprocket 16 is fixed on the other sidesurface of the ratchet wheel 12.

In operation of this embodiment, during pedal driving, the pedal crank10 drives the ratchet wheel 12 to rotate through the one-way freewheel13, so that the sprocket 16 fixed on the ratchet wheel 12 rotatessimultaneously, and propels the bicycle to move forward through a chaindrive (not shown) of the sprocket 16.

A second one way drive means comprising the ratchet members 15 and theratchet wheel 12 is provided in the second torque transmission pathbetween the motor shaft 4 and the sprocket 16 such that, when thesprocket 16 is being driven by the manually provided driving forcethrough the first torque transmission path, the motor shaft 4 is notcaused to rotate. The ratchet members 15 moveably disposed on the planetgear carrier 11 engage a rack of the ratchet wheel 12. The ratchetmembers 15 may have associated therewith means (not shown) forresiliently biasing free ends of said ratchet members 15 outwardly froma surface of the planet gear carrier 11 such that said free ends of theratchet members 15 engage teeth in the rack of the ratchet wheel 12.

Because of the one-way transmitting function of the second one-way drivemeans 12, 15, the rotation of the ratchet wheel 12 by the pedal 10 willnot drive the planet gear carrier 11 or the motor shaft 4 to rotate.During motor driving, the hollow shaft 4 of the motor rotates theeccentric wheel 22 of the planetary gear mechanism, and then theeccentric wheel 22 drives the planet gear 20 to revolve around the motoraxis. According to the angular position of the eccentric 22 at any timeduring rotation, the teeth of the planet gear 20 engage with thecorresponding teeth of the internal gear ring 18, so as to make theplanet gear 20 rotate in relation to the motor axis and this rotationwill be outputted by the planet gear carrier 11. The planet gear carrier11 rotates the ratchet wheel 12 by means of the ratchets 15 disposed onthe ratchet seats, and then the ratchet wheel 12 rotates the sprocket 16which is fixed together with the ratchet wheel 12, so as to propel thebicycle to move forward by the chain. At this time, because of theone-way transmitting function of the first one-way transmitting means,(i.e. the one-way freewheel 13), the rotation of the sprocket 16 willnot make the pedal crank 10 or the pedal spindle 1 rotate.

In this embodiment, the motor 5 is arranged concentrically around thepedal spindle 1 such that the pedal spindle 1 is freely accommodatedthrough the hollow bore of the motor shaft 4 and such that their axes ofrotation are parallel and preferably coaxial, i.e. the pedal spindle 1and the motor shaft 4 share the same axis of rotation.

This arrangement results in a neat and compact integration of the motorwith the pedal spindle and sprocket assembly.

Also in this embodiment, the planet gear 20 is rotatably supported onthe eccentric wheel 22 whereby the planet gear 20 is made to rotate asthe eccentric wheel 22 rotates and whereby the position of the axis ofrotation of the planet gear 20 changes relative to the axis of rotationof the motor shaft 4 as the planet gear 20 rotates such that the varyingposition of the axis of rotation of the planet gear 20 defines a circlecentred on the axis of rotation of the motor shaft 1, said circle havinga radius equal to the predetermined offset amount. The planet gear 20has a smaller diameter than the internal ring gear 8, the internal ringgear 8 having a central axis co-incident with the axis of rotation ofthe motor shaft 4. The planet gear 20 has a smaller number of teeth thanthe internal ring gear 8.

The planet gear 20 rotates around the inner toothed surface of the innerring gear 8 such that the outer toothed surface of the planet gear 20meshes with only a small number of teeth of the inner ring gear 8 at anypoint of time.

The planet gear carrier 11 of the planetary gear mechanism transfers themotor provided driving force to the sprocket 16 and, in doing so,provides a neat and efficient way of mechanically transferring the motordriving force to the sprocket 16.

The planetary gear mechanism includes a counterbalance member 24 whichis configured to counterbalance an imbalance of weight caused by theoffsetting of the planet gear 20 with respect to the axis of rotation ofthe motor shaft 4. The counterbalance member 24 comprises a generallysemi-circular weighted member which is arranged to rotate with theplanet gear 20 so as to counterbalance the planet gear when the planetgear is rotating.

The motor 5 comprises an electric motor powered by a battery packcarried on the pedal driven apparatus.

FIG. 5 depicts a second embodiment of the motor and sprocket assemblyaccording to the invention. In the description of this embodiment, likenumerals to those used in FIGS. 1 to 4 are used to denote like parts,although any differences in the parts are described in the following.

In this embodiment, the second one-way drive or transmitting means,(i.e. the ratchet wheel 12 and ratchets 15), is omitted, so that theplanet gear carrier 11′ of the planetary gear mechanism is fixedlycoupled to the sprocket 16 for rotation therewith. The planet gear 20and the sprocket 16 are directly and fixedly connected with the (outputmember of) one-way freewheel 13 of the first one-way drive/transmittingmeans. As such, the planet gear carrier 11′ is modified compared to itsconfiguration in the first embodiment of FIGS. 1 to 4 to enable it to bedirectly and fixedly connected with the one-way freewheel 13. In thisembodiment, the direct coupling of the planet gear carrier 11′ to thefreewheel 13 enables the bicycle function to be altered. In thisembodiment, the motor 5 can function as a power generating device drivenby pedaling or forward motion of the bicycle, i.e. the bicyclefreewheeling down a slope, for example.

In operation of this embodiment, during pedal driving, the pedal crank10 drives the planet gear carrier 11′ and the sprocket 16 to rotatesimultaneously through the one-way freewheel 13, and then propels thebicycle to move forward through the chain. At this time, since theplanet gear carrier 11′ rotates along with the sprocket 16, it drivesthe planet gear 20 and the eccentric wheel 22 to rotate, which in turndrives the hollow shaft 4 of the motor 5 to rotate. Under thiscircumstance, if the rider intends to increase the load applied on thepedals to do exercise using the bicycle, or intends to use the motor tofunction as a brake for decelerating the bicycle when going downhill orto use the motor to generate power for lights or recharging the motorbattery pack, the rider can control a switch installed on, for example,a handlebar of the bicycle to switch the circuit of a controller so asto transform the motor 5 to a power generating device, the powergenerated by which can be utilized by a load or for charging a battery.During normal riding, the controller can be switched to be in a normalriding state, so that no additional load is applied on pedals. Duringmotor driving, the hollow shaft 4 of the motor 5 drives the eccentricwheel 22 of the planetary gear mechanism to rotate, which in turn drivesthe planet gear 20 to revolve around the axis of the motor.Consequently, torque will be outputted by the planet gear carrier 11′which drives the sprocket 16 to rotate, and then propels the bicycle tomove forward through the chain drive. At this time, due to the one-waytransmitting function of the one-way freewheel 13, the rotation of thesprocket will not drive the pedal crank 10 to rotate, i.e. the pedalcrank and the pedal spindle can freewheel.

In this example, when moving forward, the bicycle can drive the motor togenerate power through the transference of power transferring from thechain drive, whilst no one-way freewheel having the one-waydrive/transmitting function is provided at the rear wheel hub.

FIG. 6 depicts a third embodiment of the motor and sprocket assemblyaccording to the invention. In the description of this embodiment, likenumerals to those used in FIGS. 1 to 5 are used to denote like parts,although any differences in the parts are described in the following.

In this embodiment, the planetary gear mechanism does not include aweighted counterbalance member, but comprises first and second identicalplanet gears 20, 26 arranged half a revolution out of phase with eachother such that said first and second planet gears 20, 26 counterbalanceeach other on rotation. The first and second planet gears 20, 26 may belocated within respective internal ring gears, but are preferablylocated for rotation half a revolution out of phase with each otherwithin a common, single internal ring gear 8′ of double width comparedto the internal ring gear of the first or second embodiments. The firstand second planet gears 20, 26 are supportably mounted on respectivefirst and second eccentric wheels 22, 25. The second planet gear 26 ismounted on the second eccentric wheel 25 by a bearing 28. The pins 17are made longer than in other embodiments and extend through respectivesets of apertures 19, 27 in both of the planet gears 20, 26.

The use of two out of phase planet gears 20, 26 negates the need toprovide a weighted counterbalance member and provides a balanced systemwhich transfers motor driving force to the sprocket 16 more efficientlyand quietly than the foregoing arrangement including a weightedcounterbalance.

This embodiment in like manner to the second embodiment depicted by FIG.5 includes a second one way drive means 12, 15. However, it will beunderstood that the described arrangement of first and second planetgears 20, 26 of this embodiment (FIG. 6) can be employed within eitherof the first (FIGS. 1 to 4) or second (FIG. 5) embodiments with minimalmodification. Furthermore, the operation of this embodiment is otherwisethe same in all respects to the second embodiment save for the fact thatcounterbalancing of the (first) planet gear 20 is provided by the secondplanet gear 26.

In the foregoing embodiments of the invention, the teeth on the gears ofthe planetary gear mechanism are depicted as comprising spur or straightcut gears in which the edge of each tooth is straight and alignedparallel to the axis of rotation of the gear. However, in preferredembodiments, the gears comprise helical gears.

Helical gears offer a refinement over spur gears. The leading edges ofthe teeth are not parallel to the axis of rotation, but are set at anangle to said axis of rotation of the gear. Since the gear is curved,this angling causes the tooth shape to be a segment of a helix. Theangled teeth engage more gradually than do spur gear teeth causing themto run more smoothly and quietly. With parallel helical gears, each pairof teeth first make contact at a single point at one side of the gearwheel; a moving curve of contact then grows gradually across the toothface to a maximum then recedes until the teeth break contact at a singlepoint on the opposite side. In spur gears teeth suddenly meet at a linecontact across their entire width causing stress and noise. Spur gearsmake a characteristic whine at high speeds and can not take as muchtorque as helical gears. A disadvantage of helical gears is a resultantthrust along the axis of the gear, which normally needs to beaccommodated by appropriate thrust bearings, but in the presentinvention, other components of the motor transmission system act tooppose any thrust along the axis of the gear caused by meshing helicalgears and so thrust bearings may not be necessary in some embodiments.In all other respects, the planetary gear mechanism having helical gearsis the same as the embodiments of the planetary gear mechanismhereinbefore described.

FIGS. 7 to 9 depict a fourth embodiment of the motor and sprocketassembly according to the invention. In the description of thisembodiment, like numerals to those used in FIGS. 1 to 6 are used todenote like parts, although any differences in the parts are describedin the following.

In this embodiment, the arrangement of components is generally identicalto that of the third embodiment save for the gear mechanism comprising atoothless planetary gear mechanism.

The toothless planetary gear mechanism has first and second toothlessplanet gears 30, 31 whose axes of rotation are offset by a predeterminedamount with respect to the axis of rotation of the motor shaft 4. Thereduction gear ratio of the toothless planetary gear mechanism isdefined by a relationship between the respective diameters of thetoothless planet gears 30, 31 and a single, common toothless internalring gear 29 within which the first and second planet gears 30, 31 arelocated for rotation. The toothless planet gears 30, 31 have smallerdiameters than the toothless internal ring gear 29. The first and secondtoothless planet gears 30, 31 are rotatably supported respectively onfirst and second eccentric wheels 22, 25 and located within the common,single toothless internal ring gear 29 half a revolution out of phasewith each other to each counterbalance the other. The second planet gear31 is mounted on the second eccentric wheel 25 by a bearing 28. The pins17 are made longer than in other embodiments and extend throughrespective sets of apertures 19, 27 in both of the planet gears 30, 31.Outer surfaces of the first and second planet gears 30, 31 engage aninner surface of the toothless inner ring gear 29. The inner surface ofthe internal ring gear and/or the outer surfaces of the planet gears 30,31 may be roughened to enhance the coefficient of friction actingbetween said engaged surfaces at their lines of contact. The frictionfit between the first and second planet gears 30, 31 and the toothlessinternal ring gear 29 is achieved by heating the toothless internal ringgear 29 and shrink fitting it over the first and second toothless planetgears 30, 31.

One advantage of a toothless planetary gear mechanism is quietness. Thelack of gear teeth and the reliance on contact between generally smooth,although possibly roughened, surfaces to effect a transfer of power fromthe motor to the sprocket results in very quiet operation and moreefficient power transfer as there is no slippage or chatter between gearteeth as can occur in toothed gear mechanisms.

It will be understood that this embodiment could be modified to provideonly a single toothless planet gear in a similar manner to the firstembodiment depicted by FIGS. 1 to 4. In such a case, the toothlessplanetary gear mechanism would include a counterbalance memberconfigured to counterbalance an imbalance of weight caused by theoffsetting of the toothless planet gear with respect to the axis ofrotation of the motor shaft.

It will also be appreciated that, whilst this embodiment includes asecond one way drive means 12, 15 in a similar manner to the first andthird embodiments, it could be modified in a similar manner to thesecond embodiment to omit the second one way drive means and directlyand fixedly couple the planet gear carrier 11 to the first one way drivemeans 13. In such case, the planet gear carrier 11 may be affixed to anoutput member of the first one way drive means 13 for rotationtherewith, whereby the manually provided driving force applied to thepedals 10 is transferred via the first torque transmission path to themotor shaft 4 through the toothless planetary gear mechanism as well asto the sprocket 16.

FIG. 10 depicts a bicycle 40 having a motor and sprocket assembly 50according to any of the foregoing embodiments. The bicycle body may beprovided with a recess at the position of the central spindle forreceiving the motor and the gear mechanism. The assembly of the motorand the gear mechanism, together with the central pedal spindle, arereceived tightly in the recess.

It can be seen therefore that the invention provides a pedal drivenapparatus comprising: manually operable pedals fixed for rotation with apedal spindle for receiving a manually provided driving force; a motorhaving a shaft for receiving a motor provided driving force; a firsttorque transmission path for transferring the manually provided drivingforce to a sprocket of the pedal driven apparatus; a second torquetransmission path for transferring the motor provided driving force tosaid sprocket of the pedal driven apparatus; wherein a first one waydrive means is provided in the first torque transmission path betweenthe pedal spindle and the sprocket such that when the sprocket is beingdriven by the motor provided driving force through the second torquetransmission path, the pedal spindle is able to freewheel.

It can also be seen that the invention provides a motor for a pedaldriven apparatus comprising: a shaft for receiving a motor provideddriving force; and a gear mechanism mechanically coupling the motorshaft to a sprocket of the pedal driven apparatus, wherein the gearmechanism has a reduction gear ratio and operates to transfer the motorprovided driving force from the motor shaft to the sprocket at saidreduction gear ratio and wherein the motor is arranged concentricallyaround a pedal spindle of the pedal driven apparatus such that the pedalspindle is freely accommodated through a hollow bore of the motor shaftand such that their axes of rotation are parallel.

And it can be seen that the invention provides a sprocket assembly for apedal driven apparatus, comprising: a sprocket; first means formechanically coupling the sprocket to a pedal driven pedal spindle; andsecond means for mechanically coupling the sprocket to an output shaftof a motor, wherein the first mechanical coupling means includes a firstone way drive means coupling the pedal spindle and the sprocket suchthat the first one way drive means transfers a manually provided drivingforce applied to the pedals of the pedal driven apparatus to thesprocket to cause rotation of the sprocket and allows the pedal spindleto freewheel when the sprocket is being driven by the motor outputshaft.

As compared with known motor assisted bicycles, the invention has atleast the following advantages:

1) The present invention uses a specially designed motor having a hollowshaft which is directly connected with a reduction planetary gearmechanism and which, due to the fact that the planet gear has fewerteeth or a smaller diameter than the ring gear, a sufficienttransmission ratio can be obtained with the smallest space size.Therefore all of the parts together with the pedal central spindle canbe constituted as a coaxial driving assembly, so that the structure iscompact, the bicycle is light in weight, and its operation is moreflexible;

(2) The present invention can be used in combination with a standardexternal transmission or internal transmission installed on the rearwheel of a bicycle, for either pedal driving or motor driving. The speedratio can be varied during the riding of the bicycle so that the bicyclecan be operated at the best driving efficiency with various ranges ofspeed on either hills or flats;

(3) The present invention is very practical, and can be directlyinstalled on an existing bicycle after having the central spindlethereof modified slightly;

(4) With driving modes based on the above structure, it can reduce arider's effort during riding;

(5) The present invention can be partially modified so as to become anexercise bicycle having a power generation function and other functionssuch as the battery can be charged by the inertial moment of the bicyclewhen going downhill or by the user pedaling; and

(6) The present invention is novel in structure, simple in profile, andcan be applied to various types of electric bicycles or electricassisted bicycles.

In general, the invention provides a hybrid bicycle which can bemanually propelled, but which includes a motor unit for also causingforward propulsion of the bicycle. The bicycle comprises manuallyoperable pedals fixed for rotation with a pedal spindle for receiving amanually provided driving force and a motor having a shaft for receivinga motor provided driving force. A first torque transmission path isprovided for transferring the manually provided driving force to asprocket of the pedal driven apparatus and a second torque transmissionpath is provided for transferring the motor provided driving force tosaid sprocket of the pedal driven apparatus. A first one way drive meansis also provided. This is provided in the first torque transmission pathbetween the pedal spindle and the sprocket such that when the sprocketis being driven by the motor provided driving force through the secondtorque transmission path, the pedal spindle is able to freewheel. Thesecond torque transmission path may include a gear mechanismmechanically coupling the motor shaft to the sprocket of the pedaldriven apparatus. The gear mechanism has a reduction gear ratio andoperates to transfer the motor provided driving force from the motorshaft to the sprocket at said reduction gear ratio. The motor may bearranged concentrically around a pedal spindle of the pedal drivenapparatus such that the pedal spindle is freely accommodated through ahollow bore of the motor shaft and such that their axes of rotation areparallel and preferably co-incident.

The invention claimed is:
 1. A motor unit comprising: a motor shaft forreceiving a motor provided driving force; an auxiliary shaft forreceiving an externally provided driving force: a first torquetransmission path for transferring the externally provided driving forceto a drive mechanism; a second torque transmission path for transferringthe motor provided driving force to said drive mechanism, the secondtorque transmission path comprising the motor shaft and a gear mechanismmechanically coupling the motor shaft to the drive mechanism; wherein afirst one way drive means is provided in the first torque transmissionpath between the auxiliary shaft and the drive mechanism such that whenthe drive mechanism is being driven by the motor provided driving forcethrough the second torque transmission path, the auxiliary shaft is ableto freewheel, wherein the gear mechanism has a reduction gear ratio andoperates to transfer the motor provided driving force from the motorshaft to the drive mechanism at said reduction gear ratio, the gearmechanism comprising a planetary gear mechanism having a planet gearwhose axis of rotation is offset by a predetermined amount with respectto the axis of rotation of the motor shaft; the planet gear beingrotatably supported on an eccentric wheel whereby the planet gear ismade to rotate as the eccentric wheel rotates and whereby the positionof the axis of rotation of the planet gear changes relative to the axisof rotation of the motor shaft as the planet gear rotates such that thevarying position of the axis of rotation of the planet gear defines acircle centered on the axis of rotation of the motor shaft, said circlehaving a radius equal to the predetermined amount.
 2. The motor unit ofclaim 1, wherein the motor shaft is arranged concentrically around theauxiliary shaft such that the auxiliary shaft is freely accommodatedthrough a hollow bore of the motor shaft and such that their axes ofrotation are parallel.
 3. The motor unit of claim 2, wherein theauxiliary shaft and the motor shaft share the same axis of rotation. 4.The motor unit of claim 1, wherein the first torque transmission pathcomprises the auxiliary shaft for receiving an externally provideddriving force and the first one way drive means, wherein the first oneway drive means mechanically couples the auxiliary shaft to the drivemechanism such that the first one way drive means transfers theexternally provided driving force to the drive mechanism and wherein thefirst one way drive means allows the auxiliary shaft to freewheel whenthe drive mechanism is being driven by the motor shaft.
 5. The motorunit of claim 4, wherein the first one way drive means comprises afreewheel device.
 6. The motor unit of claim 1, wherein the planet gearhas a smaller diameter than an internal ring gear within which itlocates for rotation therewithin, the internal ring gear being fixed inposition and having a central axis co-incident with the axis of rotationof the motor shaft, the planet gear having a smaller number of teeththan the internal ring gear.
 7. The motor unit of claim 6, wherein theplanet gear is rotatably supported on the eccentric wheel by a bearing.8. The motor unit of claim 6, wherein a planet gear carrier of theplanetary gear mechanism is configured to transfer the motor provideddriving force to the drive mechanism.
 9. The motor unit of claim 8,wherein the planet gear carrier is affixed to the drive mechanism forrotation therewith.
 10. The motor unit of claim 9, wherein the planetgear carrier is also affixed to an output member of the first one waydrive means for rotation therewith, whereby the externally provideddriving force is transferred via the first torque transmission path tothe motor shaft through the planetary gear mechanism as well as to thedrive mechanism.
 11. The motor unit of claim 1 wherein the planetarygear mechanism includes a counterbalance member which is configured tocounterbalance an imbalance of weight caused by the offsetting of theplanet gear with respect to the axis of rotation of the motor shaft. 12.The motor unit of claim 11, wherein the counterbalance member comprisesa generally semi-circular weighted member which is arranged to rotatewith the planet gear so as to counterbalance the planet gear when theplanet gear is rotating.
 13. The motor unit of claim 1, wherein theplanetary gear mechanism does not include a weighted counterbalancemember, but comprises first and second identical planet gears arrangedhalf a revolution out of phase with each other such that said first andsecond planet gears counterbalance each other on rotation.
 14. The motorunit of claim 13, wherein the first and second planet gears are locatedfor rotation half a revolution out of phase with each other within acommon, single internal ring gear.
 15. The motor unit of claim 13,wherein each of the first and second planet gears are supportablymounted on respective first and second eccentric wheels.
 16. The motorunit of claim 1, wherein the gear mechanism comprises a toothlessplanetary gear mechanism having a toothless planet gear whose axis ofrotation is offset by a predetermined amount with respect to the axis ofrotation of the motor shaft and wherein the reduction gear ratio of thetoothless planetary gear mechanism is defined by a relationship betweenthe respective diameters of the toothless planet gear and a toothlessinternal ring gear within which the planet gear is located for rotation,the toothless planet gear having a smaller diameter than the toothlessinternal ring gear.
 17. The motor unit of claim 16, wherein thetoothless planet gear is rotatably supported on an eccentric wheelwhereby the toothless planet gear is made to rotate as the eccentricwheel rotates and whereby the position of the axis of rotation of thetoothless planet gear changes relative to the axis of rotation of themotor shaft as the toothless planet gear rotates such that the varyingposition of the axis of rotation of the toothless planet gear defines acircle centred on the axis of rotation of the motor shaft, said circlehaving a radius equal to the predetermined offset amount.
 18. The motorunit of claim 17, wherein the toothless internal ring gear is fixed inposition and has a central axis co-incident with the axis of rotation ofthe motor shaft.
 19. The motor unit of claim 18, wherein the toothlessplanet gear is rotatably supported on the eccentric wheel by a bearing.20. The motor unit of claim 18, wherein a planet gear carrier of thetoothless planetary gear mechanism is configured to transfer the motorprovided driving force to the drive mechanism.
 21. The motor unit ofclaim 20, wherein the planet gear carrier is affixed to the drivemechanism for rotation therewith.
 22. The motor unit of claim 21,wherein the planet gear carrier is also affixed to an output member ofthe first one way drive means for rotation therewith, whereby theexternally provided driving is transferred via the first torquetransmission path to the motor shaft through the toothless planetarygear mechanism as well as to the drive mechanism.
 23. The motor unit ofclaim 17, wherein the toothless planet gear is rotatably supported onthe eccentric wheel with its axis of rotation is offset by apredetermined amount with respect to the axis of rotation of the motorshaft and located within the toothless internal ring gear to engage atoothless inner ring gear surface by heating the toothless internal ringgear and shrink fitting it over the toothless planet gear.
 24. The motorunit of claim 16, wherein the toothless planetary gear mechanismincludes a counterbalance member which is configured to counterbalancean imbalance of weight caused by the offsetting of the toothless planetgear with respect to the axis of rotation of the motor shaft.
 25. Themotor unit of claim 24, wherein the counterbalance member comprises agenerally semi-circular weighted member which is arranged to rotate withthe toothless planet gear so as to counterbalance the toothless planetgear when the toothless planet gear is rotating.
 26. The motor unit ofclaim 16, wherein the toothless planetary gear mechanism does notinclude a weighted counterbalance member, but comprises first and secondidentical toothless planet gears arranged half a revolution out of phasewith each other such that said first and second toothless planet gearscounterbalance each other on rotation.
 27. The motor unit of claim 26,wherein the first and second toothless planet gears are located forrotation half a revolution out of phase with each other within a common,single toothless internal ring gear.
 28. The motor unit of claim 26,wherein each of the first and second toothless planet gears aresupportably mounted on respective first and second eccentric wheels. 29.The motor unit of claim 26, wherein the first and second toothlessplanet gears are rotatably supported respectively on the first andsecond eccentric wheels with their axes of rotation offset by apredetermined amount with respect to the axis of rotation of the motorshaft and located within a common, single toothless internal ring gearfor rotation half a revolution out of phase with each other to engage atoothless inner ring gear surface by heating the toothless internal ringgear and shrink fitting it over the first and second toothless planetgears.
 30. The motor unit of claim 1, wherein a second one way drivemeans is provided in the second torque transmission path between themotor shaft and the drive mechanism such that when the drive mechanismis being driven by the externally provided driving force through thefirst torque transmission path, the motor shaft is not caused to rotate.31. The motor unit of claim 30, wherein the second one way drive meanscomprises at least one ratchet member moveably disposed on the planetgear carrier and arranged to engage a rack of a ratchet wheel fixed torotate with the drive mechanism.
 32. The motor unit of claim 31, whereinthe at least one ratchet member has associated therewith means forresiliently biasing a free end of said ratchet member outwardly from asurface of the planet gear carrier such that said free end of theratchet member engages a tooth in the rack of the ratchet wheel.
 33. Themotor unit of claim 1, wherein the motor unit comprises a part of apedal driven apparatus.
 34. The motor unit of claim 1, wherein the motorunit is an electric motor powered by a battery pack carried on a pedaldriven apparatus.
 35. A pedal driven apparatus having a motor unitaccording to claim 1, wherein said externally provided driving force isa manually provided driving force provided by manually operable pedalsof said apparatus which are fixed for rotation with the auxiliary shaft,said auxiliary shaft comprising a pedal spindle; and wherein said drivemechanism comprises a sprocket, said first torque transmission pathbeing arranged to transfer the manually provided driving force to saidsprocket and said second torque transmission path being arranged totransfer the motor provided driving force to said sprocket; and whereinthe first one way drive means is provided in the first torquetransmission path between the pedal spindle and the sprocket such thatwhen the sprocket is being driven by the motor provided driving forcethrough the second torque transmission path, the pedal spindle is ableto freewheel.